1. Field of the Invention
The present invention relates to an improvement in a structure of a solid state image sensing device used in an image forming apparatus such as a copy machine, printer, facsimile machine and so on or an image input apparatus utilized in an image scanner.
2. Description of the Prior Art
In an image scanner or an image forming apparatus such as copy machine, printer, facsimile machine and the like, an image input apparatus (image sensing apparatus) to input an optical image of an object as a target to be image picked up is equipped, and in the image input apparatus a solid state image sensing device (charge coupled device, hereinafter referred to as CCD) is used.
FIGS. 13(A) and 13(B) are of a schematic illustration and its perspective view to show a layout of image focusing optical system which constitutes an image input apparatus, and the image focusing optical system includes a solid state image sensing device 1 and a lens L, and it is arranged to face against an object D to be image picked up (manuscript copy).
In FIG. 13, the solid state image sensing device 1 is an electronic component having a structure to be equipped on a circuit board 18, in that an incoming light receiving surface is arranged to be located at a position at which optical image of the object to be image picked up D is focused by the lens L.
At the same time, in FIG. 13(B), the solid state image sensing device 1 is mounted on a surface of the circuit board 18 in the image input apparatus. Herein, the circuit board 18 has a function to drive the solid state image sensing device 1, to give an electrical process on output signal from the solid state image sensing device 1 which is generated in connection with a receiving of the optical image and then to output the processed signal to a control portion of the image input apparatus body (not shown).
At this time, especially when the object D to be image picked up in this case is a photographic image for the image input apparatus, on a semiconductor chip 3 which constitutes the solid state image sensing device 1 used a plurality of micro photoelectric conversion elements 3a are arranged in a single line. By this arrangement the image is input as a line image by the photoelectric conversion elements 3a. Especially, in the color photographic image input apparatus to input a color photographic image, a color semiconductor chip 3 is used in that three lines 3a, 3b and 3c of pixels respectively having a peak of the spectral sensitivity in Red area (hereinafter referred to as simply R), Green area (hereinafter referred to as simply G) and Blue area (hereinafter referred to as simply B) as shown in FIG. 13(C) are disposed.
Further, the image sensing device 1 is classified in a several kind by their external structure (package structure). Among all of them recently a solid state image sensing device of Ceramic Dual Inline Package (hereinafter refereed to as xe2x80x9cCer DIPxe2x80x9d) type and a solid state image sensing device with resin made package are increased because of its advantage in manufacturing cost (cheap) and they become popular to be used in the image input apparatus.
FIGS. 14(A), (B) and (C) are a plan view, a back view and a cross sectional view taken along the Axe2x80x94A line to show a basic structure of a normal (conventional) laminated type solid state image sensing device 1A (for color).
The laminated type solid state image sensing device 1A has a structure in which a semiconductor chip 3 is accommodated in a package 2 and photoelectric conversion elements are mounted on the semiconductor chip 3. The package 2 includes a package body 5 which is made of ceramic thin plates having a predetermined shape being laminated in a box form; a semiconductor chip 3 on which the photoelectric conversion element is mounted, is received in a concave portion 6 of the package body 5; lines of photoelectric conversion element 3a, 3b and 3c which are disposed on the incoming light receiving surface of the semiconductor chip 3; and a transparent cover glass 15 to seal an opening of the concave portion 6 of package body 5.
The package body 5 mounts the semiconductor chip 3 in an inner bottom (on an upper surface of the bottom plate) of the concave portion 6 and has a lead frame 7 which is brought out with passing through side walls of the package body 5, and inner end portion of the lead frame 7 is electrically connected to electrodes of the semiconductor chip 3 by lead wires 8.
Next FIGS. 15(A), (B) and (C) show a basic structure of a normal (conventional) Cer DIP type solid state image sensing device 1B (herein for color). The Cer DIP type solid state image sensing device 1B has a structure in which a semiconductor chip 3 is received in a package 2 and the photoelectric conversion elements are mounted on the semiconductor chip 3. The package 2 includes a package body 5; a semiconductor chip 3 on which the photoelectric conversion elements are mounted, is received in a concave portion 6 of the package body 5; lines of photoelectric conversion elements 3a, 3b and 3c which are disposed on the incoming light receiving surface of the semiconductor chip 3; and a transparent cover glass 15 to seal an opening of the concave portion 6 of the package body 5.
The package body 5 has a structure in which an annular window frame 10b made of ceramic is bonded to be integrated as a unit on one surface of a plate formed base frame (bottom plate) 10a made of ceramic through a sealing glass 10c, and at the same time a lead frame 7 is included in a state that the lead frame is brought out with passing through the sealing glass 10c and the lead frame 7 is electrically connected to electrodes of the semiconductor chip 3 mounted on an inner bottom of the concave portion by lead wires 8.
FIG. 16 shows a cross sectional shape of a basic structure of a solid state image sensing device 1C (in this case for color) of a resin packaging type. A package 2 of this solid state image sensing device 1C has a structure in that a semiconductor chip 3 is mounted via a metal plate 12 on an inner bottom surface of a concave portion 11a in a resin packaging body 11, photoelectric conversion elements are mounted on the semiconductor chip 3 and the electrode on the semiconductor chip are connected through lead wires (bonding wires) 8 to a lead frame 7 which is disposed in such a manner to pass through side walls of the packaging body 11.
Usually a thermosetting resin is used for the resin packaging body 11. An opening in the concave portion 11a is scaled by a cover glass 15.
Herein the image sensing device 1 is usually mounted on the circuit board 18 by means that the lead frames 7 is soldered on a wiring pattern of the circuit board 18 as shown in FIG. 13(A), and the circuit board 18 is mounted on a housing body and so on which is attached on the image input apparatus (image sensing apparatus).
However, it is difficult to mount the solid state image sensing device 1 with high precision on a predetermined position of the circuit board 18 because it has a soldered structure on the circuit board. Though the circuit board 18 can be mounted accurately on the image input apparatus, incorrectness of positions between the solid state image sensing device 1 and the circuit board 18 sometimes brings an error of positional alignment between the solid state image sensing device 1 and the component parts such as the lens L and the like as a result.
The error of positional alignment of this kind brings a severe error in positional alignment between the solid state image sensing device 1 and an image of the manuscript copy D as an object to be image picked up, and accordingly causes an image sensing quality deterioration.
Next FIGS. 17(A) and (B) show a structure of holding means (chucking means) to be used for holding the solid state image sensing device when the solid state image sensing device 1 is mounted on the circuit board 18.
Holding means 50 has a pair of holding portions 51 which are supported capable of reciprocating in a direction shown by the arrow located at a top portion of a working arm which is not shown in the drawing, a positional alignment is performed by that the solid state image sensing device 1 is moved and mounted on the circuit board 18 in a state that predetermined portions of the package of the solid state image sensing device 1 are held by holding surfaces 51a of the respective holding portions 51. However, a provability of performing accurate positional alignment on the circuit board with high precision is never enough because sufficient attention has not been paid for an attitude or portions when an outer surface of the solid state image sensing device 1 is made to abut with the holding surfaces 51a of the holding means 51.
Because of these facts, the applicant of the present invention has proposed an adjusting method for positional relation of the solid state image sensing device 1 on the circuit board 18 in that the solid state image sensing device 1 is given micro motions along five axes of X, Y, Z, xcex2 and xcex3 as shown in FIG. 13(B) in at the stage of manufacturing of the image input apparatus in order to make the line images which are focused by the lens L being located accurately on the solid state image sensing device 1 and at the same time to read out optical characteristics (focus, magnification and the like) with a predetermined required accuracy.
The solid state image sensing device 1 that has been achieved the positional adjustment as described above is attached on a holding member which is mounted on the image input apparatus by means of a fixing means such as adhesion, screw and so on.
However, it is not easy to achieve a fixing the solid state image sensing device 1 with a high degree of accuracy in order to make the line images which are focused by the focusing lens L being located accurately on the solid state image sensing device 1 and at the same time to read out optical characteristics with a predetermined required accuracy when the solid state image sensing device 1 has been achieved the positional adjustment along the five axes in a positional adjustment process before the solid state image sensing device 1 is adhered and fixed, and there has been no proposals of concrete structure to raise the manufacturing yield or to prevent an occurrence of deterioration of fixing force for the solid state image sensing device 1.
In Japanese Patent Publication No. Hei 05 (1993)-226493 titled in xe2x80x9cGlass Sealed Type Integrated Circuitxe2x80x9d a structure that glass meniscus surface (it means side wall of the sealing glass) is made in convex form, is disclosed to prevent an occurrence of cracks at the sealing glass. Also in Japanese Patent No. 2576694 titled in xe2x80x9cSemiconductor Apparatusxe2x80x9d a structure that a length of the window frame (cap) is made longer than that of a base is disclosed to increase an adhesive strength by a wider adhering area.
The package structure disclosed in each of these patents and patent publications seems to be similar to a structure of the present invention which will be described later, however the parts disclosed in the publications are not the solid state image sensing device.
That is to say the semiconductor chip which is built in the package is not the photoelectric conversion element but a storage element such as memory (ROM and the like). In other words a necessity of precise positional adjustment is not found when these parts are mounted on the circuit board in some kind of electronic equipment and so on because they are the storage element. In short, the technical problem is quite different from that of the present invention, namely, a standard for assembling. Accordingly the package for the storage element which are disclosed in the above described publications, do not have the structure to be employed as a standard for assembling.
The present invention has been made in reference to the above described problems, it is one object of the present invention to provide a supporting structure for the solid state image sensing device by that a cost reduction is realized by eliminating complicated mechanism element to the utmost, the package can be mounted on the circuit board with a high degree of accuracy so as to raise the manufacturing yield, and at the same time an occurrence of the deterioration of quality after the product has been manufactured is prevented, a fixing the solid state image sensing device with a high degree of accuracy in order to make the line images which are focused by the focusing lens being located accurately on the solid state image sensing device is achieved and at the same time reading out of the optical characteristics (focus, magnification) with a predetermined required accuracy is achieved, and the position of it can be adjusted by the micro motions along the five axes of X, Y, Z, xcex2 and xcex3 before the solid state image sensing device is adhered and fixed.
To solve the above described problems, a solid state image sensing device in accordance with the present invention is characterized by that the solid state image sensing device including a semiconductor chip to image sensing which has at least one of photoelectric conversion element line; and a package into which the semiconductor chip is received, and the package is composed of an insulating package body which has a concave portion on the upper surface and the semiconductor chip mounted on a flat inner bottom surface of the concave portion; a transparent cover glass to be fixed on an upper surface of outer frame of the concave portion of the package body for sealing the concave portion; and a lead frame which is connected to electrodes on the semiconductor chip within the package body and is brought out to outside of the package body, further the solid state image sensing device has a reference plane for attaching onto an image input apparatus is arranged on the package, and the reference plane for attaching is made parallel to the inner bottom surface of the concave portion on which the semiconductor chip is mounted.
The above described reference plane for attaching is characterized by a surface which is located orthogonally to a light axis along which an optical image comes into an incoming light receiving surface of the semiconductor chip through the cover glass.
The above described package is characterized by composed of the package body including a base frame which is made of flat ceramic plate to constitute the bottom plate; and an annular window frame made of ceramic to be fixed on one of surface of the base frame through a sealing glass; a transparent cover glass to be fixed on upper surface of outer frame of the window frame; and a lead frame which is brought out outwardly passing through the sealing glass.
The above described package body is characterized by made of resin; the device having a structure in that the semiconductor chip is mounted on a metal plate located on the bottom surface of the concave portion of the package body; the reference plane for attaching onto the image input apparatus being arranged on the metal plate.
The above described reference plane for attaching onto the image input apparatus is characterized by arranged on an upper surface of the cover glass.
The above described reference plane for attaching onto the image input apparatus is characterized by arranged on an upper surface or the outer frame of the concave portion of the package body or an upper surface of the window frame.
The above described reference plane for attaching onto the image input apparatus is arranged on a bottom surface of the concave portion of the package body or on an upper surface of the base frame.
The above described reference plane for attaching onto the image input apparatus is characterized by arranged on a protruding surface which is made any one of the bottom plate of the package body, the base frame or the metal plate protruding to any one of direction.